This invention pertains to agitation of water for increasing levels of dissolved Oxygen for the purpose of sustaining increased growth of aerobic organisms.
The amount of organisms that can be supported by any particular environment is dependant on the available resources found within that environment. The ability of an environment to support life, and the concentration of the population, is governed by limiting factors. In a terrestrial environment, the limiting factors are usually the concentration of nutrients and the amount of space available to the organism in question. In an aqueous environment, the amount of dissolved Oxygen is an additional limiting factor when considering growth of aerobic organisms.
It is generally known that higher levels of dissolved Oxygen exist in water that is turbulent. Thus, turbulent water is able to support a higher concentration of aerobic life than standing water. Less active water will contain less dissolved Oxygen and will thus support a lower concentration of aerobic life.
When considering a body of water that is inactive or stagnant, such as a pond or a standing tank, the amount of dissolved Oxygen may be low in concentration. Additionally, stratification within a body of water can arise due to stagnation or a decreased amount of turbulence. Stratification is manifested as distinct bands of water in which the temperature may vary significantly from one band to the next. As is generally known, water of different temperatures will have different solubility factors for molecules such as Oxygen. These variances can be detrimental to aquatic life. Water that is colder will have a lower solubility for Oxygen and therefore be less capable of supporting particular kinds and/or amounts of aquatic aerobic life. Aerobic life in these situations is limited by the amount of Oxygen available for respiration. In situations where high concentrations of aerobic life are desirable, control of the amount of dissolved Oxygen as a limiting factor is extremely important. Accordingly, maintaining a consistent temperature or a temperature that varies within certain parameters is an important consideration when attempting to establish an optimum growth environment.
Introduction of air, and thus Oxygen, into aqueous environments using artificial means has been utilized for many years. The most common example would be aeration using an air pump to bubble air, and thus Oxygen, through the standing water of a recreational fish tank. In an industrial setting, aeration of water is performed by either spraying water into the air using jets or by agitating the water using paddles or brushes. All of these examples accomplish the common goal to varying degrees of introducing air bubbles into the water, thus increasing the amount of surface to air contact and therefore increasing the opportunity of dissolving Oxygen into the water.
In addition to the introduction of Oxygen into the water, aerators also help to destratify water by causing turbulence, thus mixing the different temperature bands and creating a more unified environmental temperature. The success of this is dependant on the power of the aerator/destratifier and the depth of the body of water.
Most of the agitating aerators in use today utilize one or more mechanical paddle wheels, with paddles attached to external drive shafts and employ external floatation devices. Motors are mounted externally on a frame which exposes them to possible damage from water and atmospheric conditions.
Exposure to the elements produces many problems with current aerators using external parts. Metal parts become weakened from erosion and rust, and must be serviced or replaced periodically. Moving parts such as bearings and shafts, must be lubricated often because of their constant exposure to water. Periodic cleaning is necessary to remove calcium and algae deposits that continuously build up on the aerators.
Engineering problems also plague currently available aerators. The motor providing the power source for the aerators may be either on board or remote from the paddle wheel. Aerators using a remote motor must have a power delivery system to the paddle wheel. Aerators using on-board motors as power sources must have a way to secure and protect the motor. External on-board motors must have weatherproof casings to protect the motors from the elements. Aerators using on-board motors must utilize a floatation device buoyant enough to support the additional weight of the motor.
Due to the shallow depth of the water in which the aerators are being used, there is a limitation to the size of the floatation device and the motor. The efficiency of a device to aerate water is generally expressed as pounds of dissolved Oxygen per horsepower per hour. Increasing the horsepower will increase the amount of dissolved Oxygen. However, increasing the horsepower will also increase the size and weight of the motor and gearbox. Increasing the size and weight of the motor and gearbox will require a larger support system. Therefore, floating aerators with external on-board motors have a reduced efficiency due to the limitation on the size of motor and gearbox that can be used and how they are attached to the paddle drum.
In the fishery industry, more precisely, the catfish industry, the amount of dissolved Oxygen directly affects the quantity of fish in a population as well as the size of the catfish. To increase the percent yield of any particular fish farm, the water has to be agitated to prevent stagnation, increase dissolved Oxygen, and to prevent stratification. The amount of horsepower necessary to accomplish these goals vary according to the size of the pond or holding tank as well as the population of fish present.
With respect to wastewater treatment, high levels of dissolved Oxygen are required to maintain maximum aerobic respiration. Wastewater treatment using aerobic microorganisms requires constant aeration of the wastewater liquor. Wastewater treatment currently favours the use of microorganisms such as bacteria for biological decomposition of waste material into harmless or useful products. Bacterial respiration may involve aerobic and/or anaerobic bacteria. Anaerobic bacteria do not tolerate high levels of Oxygen and in fact, high concentrations of Oxygen are detrimental to anaerobic bacterial populations.
Respiration by anaerobic bacteria generally produces undesirable noxious odors and is a slower process than aerobic respiration. Conversely, aerobic respiration is a faster process and the final products are not usually noxious. For example, aerobic respiration of organic waste would yield carbon dioxide and water, as well as the oxidized waste material. Thus, increasing the concentration of dissolved Oxygen in wastewater would reduce the population of anaerobic bacteria and increase the population of aerobic bacteria.
In the case of stagnant wastewater, bacterial respiration depletes the concentration of Oxygen present in the wastewater. Thus, as aerobic bacteria respire, the concentration of Oxygen decreases, hence, the concentration of aerobic bacteria, able to flourish in this environment, decreases. The lack of Oxygen would then allow the concentration of anaerobic bacteria to increase. Since anaerobic respiration is a less desirable form of wastewater treatment, methods of adding Oxygen to the wastewater are required.
It is the object of this invention to provide an improved aeration device capable of using an internally mounted on-board motor and gearbox, and capable of creating greater turbulence and thus delivering a greater Oxygen transfer than previously possible.
It is a further object of this invention to provide aeration paddles of unique design and construction for improved turbulence and increased Oxygen transfer.
The aerators according to the present invention overcome the deficiencies of previous aerators by providing an aerator having a smaller raft type device with a frame and floatation, a non-floating drum mounted on the frame, the drum having a plurality of externally mounted paddles affixed along the length of the outer surface of the drum. The interior of the drum is sealed and has an internally mounted motor and gearbox, mounted inside the drum and which turns the drum. The drum is connected to a frame by a fixed stationary shaft extending through the drum and mounted therein in sealed bearings. The shaft is fixed to the frame.
Other objects, features and advantages of this invention will become obvious upon reference to the following detailed description of the invention and the drawings illustrating the preferred embodiments thereof.